61 lines
1.9 KiB
C++
61 lines
1.9 KiB
C++
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/*
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* Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "common_audio/fir_filter_c.h"
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#include <string.h>
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#include <memory>
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#include "rtc_base/checks.h"
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namespace webrtc {
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FIRFilterC::~FIRFilterC() {}
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FIRFilterC::FIRFilterC(const float* coefficients, size_t coefficients_length)
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: coefficients_length_(coefficients_length),
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state_length_(coefficients_length - 1),
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coefficients_(new float[coefficients_length_]),
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state_(new float[state_length_]) {
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for (size_t i = 0; i < coefficients_length_; ++i) {
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coefficients_[i] = coefficients[coefficients_length_ - i - 1];
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}
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memset(state_.get(), 0, state_length_ * sizeof(state_[0]));
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}
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void FIRFilterC::Filter(const float* in, size_t length, float* out) {
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RTC_DCHECK_GT(length, 0);
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// Convolves the input signal |in| with the filter kernel |coefficients_|
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// taking into account the previous state.
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for (size_t i = 0; i < length; ++i) {
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out[i] = 0.f;
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size_t j;
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for (j = 0; state_length_ > i && j < state_length_ - i; ++j) {
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out[i] += state_[i + j] * coefficients_[j];
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}
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for (; j < coefficients_length_; ++j) {
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out[i] += in[j + i - state_length_] * coefficients_[j];
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}
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}
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// Update current state.
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if (length >= state_length_) {
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memcpy(state_.get(), &in[length - state_length_],
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state_length_ * sizeof(*in));
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} else {
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memmove(state_.get(), &state_[length],
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(state_length_ - length) * sizeof(state_[0]));
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memcpy(&state_[state_length_ - length], in, length * sizeof(*in));
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}
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}
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} // namespace webrtc
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